Staked type shunt connection for carbon brushes



March 2, 1948.

R. CARMICHAEL ET AL STAKED TYPE SHUNT CONNECTION FOR CARBON BRUSHES Filed Sept. 14, 1945 ATTORNEY Patented Mar. 2, 1948 CARBON BR sHss l-R b rt Carmichael, ;,Lak w od, an Arthu .W-

7 Seidler, Cleveland, Ohio, as signersto National Carbon Company, Inc a corporation of New York Application September 14, 1945, Serial No. 616,232

4- Clain1s. (01. 1ZL-325) This invention pertains to .cpmmutator brushes or current collecting devicesof carbon or graphite for use in electric machines and moreyparticularly to shunt connections.

In the past, it hasbeencommonpractice to userivets, screws, bolts orsolder tosecureaan electrical conductor either to .a carbon brushor to a clip which in turn is .secured to a carbon brush, to use various .shapes of clips made of difierent conducting materials, to use various forms-of welding iorattaching a conductor to a clip and many other. ingenious .ways too numerous to mention. Regardless of the method used, the principal common objective-is .a shunt connection whichinsures good .electrical and mechanical connection between a flexible braided conductor and .a current collecting brush.

Although all existing pigtail connections have been devised with the aforementioned objective in mind, irequent -brush-failures have been experienced on marine crafts where the pigtails are subjected to corrosion b salt waterand sea air in addition to severe vibration and flexing. The need of a substantially stronger shunt connection was self-evident to overcome the exiiin difiiculties.

At first, :it was thought that welding of a flexi cond ct t atcrmin lc i which i ur is secured to a carbon brush would prove satisfactory. On the contrary, it was found that the heat generated at the point of weld and conducted away by the conductor oxidized the strands of the conductor sufiiciently to make them stiff. When the stiff conductor was subjected to frequent flexing or severe vibrations, the strands of the conductor were easily broken.

For a good electrical connection between the conductor and the brush the use of solder is most desirable. However, the tendency of molten solder to be taken up by the conductor by capillary action either during the initial application of the solder or if the solder should be melted by excessive heat due to heavy overload currents leads to an alloying effect on the strands of the conductor which tends to make them stiir and brittle. Further, when subjected to severe vibration and flexing, such a stiff conductor limits the movement of the brush.

. According to the invention an improved method of attaching an electrical conductor to a, terminal clip has been devised Which insures good mechanical and electrical connection under the most adverse conditions and lessens the possibility of brush failures.

The principal objects of this invention are to 2 provide ,animproved method of securing electrically and mechanically aflexible metallic conductor to ater-minal clipattached to a current collecting-brush; to provide a clip of such construction whichwill permit free flexingofthe conductor without injury tothe strands of the conductor; and to provide ,aclip having means for not only holding a flexible, conductor rigidly in place but also preventing moltensolderfrom beingtaken .up,by,the.strands of the conductor which causes .undesirablestiffening of the conductor. These and other objects ,Will, be i n in the description of. the invention which follows in. which:

Fig. Lisasection of a brushshowing the conductor. and clip. attached thereto;

.Fig. :2 is .a front elevation of the assembled brush;

Fig. 3 is a rear view ofthe clipcomprisingthe invention;

;Fig. ,,4 Y is a section Fig. 3;

Fig. 5 is: a; front elevation taken along line,5:5 of Fig.5;

gwFigt-fi is-a rear view of a clfp showing a modification of the invention;

,-Fig.;7, isaside view of Fig; 6; and

.Eig. 38 is a blank from which the cli 1' s fashioned.

The shunt connection comprising the invention includes, in combination with a conventional brush If), a substantially V-shaped terminal clip I l of suitable conducting material and a flexible electrical conductor I2 having a loop thereof mechanically secured in place in a channel formed by the inner surface of the apex l3 of the clip H by tongues l4 and I5 spaced a predetermined distance apart and electrically connected to the clip II by solder l6 placed between the tongues l4 and I5.

taken alon lined-J of The clip II is formed from a blank shown in Fig. 8 by bending the blank in such a manner that the edges l7 and ill of the channel formed by the inner surfaces of the apex I3 are rounded upwardly to permit easy bending of the flexible sive overload currents without melting the solder.

By crimping the tongues I4 and [5 very securely over the conductor l2, the tendency of molten solder flowing up the cable due to capillary action is minimized, thus reducing the tendency of the cable becoming still by such action.

Having securely affixed the conductor I2to the clip H, the clip is secured to the brush III by a rivet 20 Which extends through an opening in the brush and a complementary opening 2| in one side of the clip. i.

For smaller size brushes designed for use on low current machines, the clip may be constructed with only one wide tongue as shown in Figs. 6 and 7, whereas, for use with excessively high current machines, the clips may contain any number of tongues necessary to increase the contacting surfaces between the clip and the conductor in order to reduce contact resistance and to insure a good electrical connection without undue heating or arcing.

We claim:

1. In combination with an electric contact brush, an improved shunt connection comprising a V-shaped terminal clip secured thereto, a flexible electrical conductor having a portion thereof disposed between said terminal clip and said brush and lying within a channel formed by the inner surfaces of the apex of said clip, and crimping means tightly attaching said conductor to said clip, the ends of said channel being bent away from said conductor. l 2. In combination with an electric contact brush, an improved shunt connection comprising a terminal clip secured thereto and bent to form a channel for receiving a flexible electrical conductor, a flexible electrical conductor formed as a loop having a portion thereof disposed between clip underlying said loop and mechanically securing said loop in said channel, the ends of said channel being bent away from said loop, and said tongues being spaced apart a predetermined distance to permit introduction of solder in order to join electrically the surfaces of said conductor and said clip.

said terminal clip and said brush and lying within said channel, said terminal clip having at least one tongue lanced from said clip underlying said 4. In combination with an electric contact brush, an improved shunt connection comprising a terminal clip secured thereto and bent to form a channel for receiving a flexible electrical conductor, a flexible electrical conductor formed as a loop and having a portion thereof disposed between said terminal clip and said brush and lying Within said channel, said terminal clip having at least two tongues lanced from said clip underlying said loop and mechanically securing said loop in said channel, the ends of said channel being bent away from said loop, and said tongues being spaced apart a predetermined distance to permit introduction of solder in the area between said tongues in order to join electrically the surfaces of said conductor and said clip.

ROBERT CARMICHAEL. ARTHUR W. SEIDLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Amu- 

